Hmm... so this is what we get so far, the mixer was around about last year, you were made aware about them from the signature campaign they had, most likely not WW.money, although they probably has "monkey" or something alike in their name, you wanted to test their efficacy because you trusted this forum's reputation and thought every campaign here were vetted [they're not]. This is new account, and given you show cluelessness [not knowing what a signature campaign called, not familiar with the mixer] I'll boldly assume this is your only account and you're reading on guest mode this far, or at least that's the impression being casted here.
Now, you're someone that seemingly know what to do, given you took precaution with disposable email prior to emailing them, tails, etc. and I assume that 7 USD was meant to be a test-send, because I don't think someone will bother themselves with a concern of privacy and look for a way to mix their token for 7 USD, so yeah, most likely 7 USD in this story is for a test send.
Yet, it's quite out of character is it not, for someone who made so many step, know what to do prior to mix [those whole tails, etc.] to not being aware that 7 USD is considerably low to be mixed? Or to look for the minimum requirement? Or that have not even the slightest idea of the platform they will use, thus barely remember the name? The very same platform that managed to raise so much fury in him [for 7 USD, nonetheless] that he wanted to make a thorough post about them, but unfortunately can't do so because he procrastinate it.